/**
  * Get/Set sent status of a Order.
  *
  * @param  integer $no
  * @param  boolean $sent
  * @return boolean
  */
 public function sent($no, $sent = null)
 {
     $handle = ['orderHandle' => $this->getHandle($no)];
     if (is_null($sent)) {
         return $this->client->Order_GetIsSent($handle)->Order_GetIsSentResult;
     }
     if (!!$sent) {
         $this->client->Order_RegisterAsSent($handle);
         return true;
     }
     $this->client->Order_CancelSentStatus($handle);
     return true;
 }